The Role of the Tumor Microenvironment of Pancreatic Cancer to Predict Treatment Outcome

Background of the study: Pancreatic cancer is a highly lethal disease. Patients with resectable or borderline resectable disease may benefit from preoperative radiochemotherapy. However, only a subset of patients will respond to this potentially toxic and expensive treatment. Therefore, novel predictive markers are needed to determine treatment efficacy at an early stage. Preferably, these markers could be determined non-invasively and provide insight into the biology of pancreatic cancer. Pancreatic cancers are heterogeneous tumors. The tumor microenvironment is often characterized by large amounts of stroma, hypovascularization, and hypoxia. As these three factors can all contribute to treatment resistance, a quantitative assessment of these markers may aid in the prediction of response to preoperative radiochemotherapy. Moreover, these assessments may have prognostic value. Finally, further insight into the interrelation of these aspects of the tumor microenvironment can contribute to the evaluation of new targeted treatment options. Tumor cellularity and extracellular matrix composition can be assessed non-invasively in vivo by diffusion weighted magnetic resonance imaging (DWI) and tumor vascularity can be assessed by dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). Finally, tumor hypoxia can be evaluated by T2\* MRI and PET-CT, using the 18F-labeled hypoxic marker HX4. Objective of the study: The primary aim of the study is to assess whether DWI, DCE-MRI, T2\*, and 18F-HX4-PET/CT predict overall survival in patients with pancreatic cancer treated with surgery and adjuvant chemotherapy or with neoadjuvant radiochemotherapy, surgery and adjuvant chemotherapy. Secondary aims of the study include the assessment of the predictive value of DWI, DCE-MRI, T2\*, and 18F-HX4-PET/CT for pathological response to neoadjuvant chemoradiation, the correlation of DWI, DCE-MRI, T2\*, and 18F-HX4-PET/CT with histopathological assessment of tumor stroma, vascularization, and hypoxia, and the assessment of the predictive value of these histopathological markers for overall survival. Study design: The target population will be recruited from the the Academic Medical Centre (AMC) and Erasmus MC. First, to assess reproducibility, patients with pancreatic cancer will undergo MRI twice, once in the AMC and once in the EMC. Next, 40 consecutive patients that will undergo surgery+adjuvant treatment will have MRI and 18F-HX4-PET/CT measurements once to assess the value of the techniques to predict outcome of standard treatment. 40 patients who will undergo preoperative radiochemotherapy will have MRI and 18F-HX4-PET/CT at baseline, and 1 week before surgery. We will assess the relative contribution of each imaging method as well as the integrated use of these methods as predictive markers for survival and pathological response to treatment. Tumor tissue from resected patients will be analyzed for markers of tumor vascularization (CD31, VEGF), hypoxia (HIF1alfa, GLUT1, CA9), and stromal activation (smooth muscle actin, markers for Hedgehog pathway activity). Results will be correlated with imaging parameters, as well as patient outcome.